1. Field of the Invention
The present invention aims principally to propose a new active agent for the prevention and/or treatment of scalp disorders, especially aesthetic disorders. In particular, the present invention relates to dandruff disorders of the scalp, in particular of a greasy scalp. The present invention is also directed towards proposing a novel cosmetic process for preventing and/or treating a dandruff condition of the scalp. The present invention also relates to an assembly or kit that is suitable for use in a process of the invention. The present invention also relates to the field of topical products, food supplements or functional foods intended for scalp care.
2. Discussion of the Background
The scalp is an epidermis that undergoes continual renewal, like the rest of the cutaneous tissue, and that is rich in sebaceous glands. Normally, the scalp is renewed by imperceptible, non-visible elimination of the superficial skin cells. However, excessive renewal of the cells of the stratum corneum of the scalp, for various reasons, may result in the formation of large, thick patches of cells which are visible to the naked eye, known as “dandruff”.
Various factors may promote the onset of dandruff. For example, mention may be made of stress, the winter period, an excess of sebum, a hydration defect or colonization of the skin or of the hair follicles by yeasts of the Malassezia spp. type. These factors especially have the common feature of causing or promoting skin inflammation. Such an inflammation reinforces the appearance or even increases the presence of dandruff.
The Malassezia sp. genus is constituted of lipophilic yeast normally present on human skin and on the skin of certain warm-blooded animals. The distribution thereof depends on age, on sebaceous gland activity and on certain pathologies. The Malassezia sp. yeast represents approximately 45% of the normal commensal flora at the surface of the scalp in individuals without dandruff, but can represent 75% of the flora in the case of dandruff, and up to 85% in the case of associated seborrhoeic dermatitis. The other microorganisms present at the surface of the scalp are micrococci and Propionobacterium. Imbalance of the scalp ecoflora is a factor that promotes or even reinforces the presence of dandruff.
Dandruff conditions are chronic, frequent, recurring conditions that are socially incapacitating owing to their obvious unattractive nature. Many factors can amplify these phenomena and result in the appearance of additional disorders, such as inflammatory conditions of the scalp. These dandruff conditions and/or inflammatory conditions of the scalp are reflected by an impairment of the barrier function of the epidermis. What is more, these conditions may give rise to sensations of itching or pruritus, resulting in scratching behaviour which amplifies the phenomenon of appearance of the dandruff.
The dandruff conditions of the scalp may be of greasy or oily type or of dry type.
The dry dandruff conditions of the scalp are more frequently manifested and are amplified during skin hydration disorders, and especially during substantial dryness of the epidermis of the scalp. Thus, the treatment of dry dandruff conditions, and the solving of the unattractive manifestations thereof, involve being able to sufficiently rehydrate the scalp.
Besides, as indicated above, the scalp is rich in sebaceous glands. It has been observed that dandruff develops more easily in the excessive presence of sebum and is more readily pruritic. Sebum secretion is a normal phenomenon which is useful for the skin and for the head of hair. Sebum protects the scalp and gives the hair a sheen by lubricating the cuticle. However, hypersecretion of sebum, or seborrhoea, may lead to disruptions, annoyances, sensations or feelings of discomfort, aesthetic disorders, or even a skin pathology. Thus, an excessive secretion of sebum promotes the appearance of a greasy or oily dandruff condition of the scalp or greasy or oily dandruff.
It has also been recently demonstrated that yeast of Malassezia type have a substantial lipase activity, resulting in the hydrolysis of sebum triglycerides so as to give fatty acids. These fatty acids are then capable of causing dandruff conditions in sensitive individuals, i.e. individuals having an impaired barrier function, and therefore more particularly susceptible to the destructive action of fatty acids on the cutaneous barrier.
Thus, the greater the presence of sebum, the more readily oily dandruff develops. Moreover, it has a tendency to be more readily pruritic.
Dandruff conditions generally respond to various local or systemic treatments. For example, various preparations comprising antimicrobial agents or keratolytic agents or keratinization regulators are commonly proposed for treating dandruff conditions. In particular, preparations combining antifungal and anti-seborrhoeic agents have been proposed in order to treat severe dandruff conditions, in particular greasy or oily dandruff conditions. The antifungal-based treatments demonstrate certain effectiveness on oily dandruff conditions.
However, the efficacy of these treatments is only suspensory and demands rigorous adherence on the part of the user (frequency of use and sufficient application time). Now, daily and long-term use of these treatments may lead to a phenomenon of dependence that reduces their efficacy. The dependence may be associated with a rebound phenomenon occurring when the treatment is stopped. The rebound phenomenon is generally manifested by hyperseborrhoea or pruritus, which are paradoxically liable to worsen the dandruff condition by impairing the barrier function of the scalp.
Moreover, the aggressiveness of certain antidandruff active agents with respect to the epidermal cells or the scalp ecoflora may also affect the scalp's barrier functions and lead to worsening of the dandruff condition.
Unpleasant side effects, such as heating or irritation phenomena, may also be manifested during the use of these treatments. These side effects may also be reflected by poor adherence to the treatments, thus reducing their efficacy.
In addition, most of the active agents usually used for treating dandruff often have an unpleasant odour that also reduces the adherence to the treatment.
Finally, the efficacy of antidandruff treatments is often slow to develop and requires rigorous application over the long term. This lag time often leads to failure to follow the treatment.
Consequently, many failures occur in the use of these treatments and can usually be attributed to the following factors: protocol not properly followed; frequency of use not adhered to; non-cosmetic appearance of the product; irritation by the washing base; application time not properly adhered to; lassitude.